[Intel-gfx] [PATCH 2/2] drm/i915: Add a FIXME about crtc !active vs. watermarks

[Daniel Vetter]

On Fri, Apr 29, 2016 at 05:31:18PM +0300, ville.syrjala at linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> When the crtc is enabled but !active, we should still compute the
> watermarks as if the planes were visible. That would make it more
> likely that the we can later transition to active without errors.
> 
> Add a FIXME to remind people that we're doing the wrong thing now.
> We should perhaps just move the wm computation for each individual plane
> into the .check_plane hook, and later we'd just combine the results from
> all active planes.
> 
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Cc: Matt Roper <matthew.d.roper at intel.com>
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

In general atomic check code shouldn't ever look at crtc->active, except
in special cases (like when checking whether a transition would work). We
still have a bit a mess in that regard.

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>

> ---
>  drivers/gpu/drm/i915/intel_display.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 5ffccf6e7f36..00059d18b0f0 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -11833,6 +11833,11 @@ int intel_plane_atomic_calc_changes(struct drm_crtc_state *crtc_state,
>  	 * Visibility is calculated as if the crtc was on, but
>  	 * after scaler setup everything depends on it being off
>  	 * when the crtc isn't active.
> +	 *
> +	 * FIXME this is wrong for watermarks. Watermarks should also
> +	 * be computed as if the pipe would be active. Perhaps move
> +	 * per-plane wm computation to the .check_plane() hook, and
> +	 * only combine the results from all planes in the current place?
>  	 */
>  	if (!is_crtc_enabled)
>  		to_intel_plane_state(plane_state)->visible = visible = false;
> -- 
> 2.7.4
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch